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Zinc
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| Quote: | Originally posted by 12AX7
Yes. The Zn-Mg system contains the brittle laves intermetallic, Zn2Mg, which is 15.7% Mg by weight.
View it as an easy way to pulverize zinc that has slightly more reactivity.
Tim |
So it can be pulverised in a mortar and pestle as magnalium can be?
Also can I use the magnesium from pencil sharpeners to make the alloy or is it not pure enough? I have mixed powdered pencil sharpener with sulfur and
ignited it and it burned very fast like when I mixed pure Mg powder with sulfur. I read somewhere that pencil sharpeners are made of a alloy of
magnesium and aluminum but I belive that the one I have is pure Mg. Does the alloy of magnesium and aluminum become dark after some time (the pencil
sharpener is very old)? Also is the alloy magnalium or some other aluminum-magnesium alloy? I don't think that it is brittle as magnalium.
[Edited on 8-5-2007 by Zinc]
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12AX7
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Pencil sharpeners...magnesium!?? That makes no sense, they would use hardened steel for the cutting edge.
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Elawr
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I have a concrete float which is apparently made almost entirely of Mg. These are available at the hardware store for around $20 as Magnesium Float.
Basically a rectangular slab of lightweight metal with a wooden handle, to use for smoothing out wet concrete.
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Zinc
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| Quote: | Originally posted by 12AX7
Pencil sharpeners...magnesium!?? That makes no sense, they would use hardened steel for the cutting edge. |
The blade if made from steel. But the other part is probably made from Mg.
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Eclectic
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More likely a Zn based "pot metal". Mg castings make no economic sense for a pencil sharpener.
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DrP
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| Quote: | Originally posted by Eclectic
More likely a Zn based "pot metal". Mg castings make no economic sense for a pencil sharpener. |
Quite.. Also, I'm sure ALL of the school kids would have a field day setting fire to their pencil sharpeners. I know I would have done.. 
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Zinc
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I don't think that they are made of Mg anymore. The one I have is very old.
A little off topic but does anyone know in what ratio should Al and Zn be mixed to obtain a alloy that shrinks at least that can be obtained with
those two metals?
[Edited on 9-5-2007 by Zinc]
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12AX7
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Shrinks how much?
I don't have a graph of (or data on) shrinkage vs. alloy, but I would imagine it's roughly linear between the two metals.
Tim
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Zinc
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| Quote: | Originally posted by 12AX7
If you want to cut the amount of copper to make it cheaper or lower-melting, the best you can do is yellow brass circa 35% (on the verge of white
(beta) brass), melting point about 1600F (870C).
Tim |
Can it be made by melting Al and adding solid Cu to it so the Cu dissolves? Will it dissolve? If yes how long would it take?
What is the lagest amount of Zn that can be added to Cu so that the alloy has a brass collor? What would be the melting point of that alloy? Can it be
made by dissolving Cu in molten Zn?
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12AX7
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What the devil does aluminum have to do with brass?
Around 35% Zn is the end of yellow brass and the beginning of beta (white) brass, with a melting point in the 1600F range. This can all be looked up
on an alloy database such as www.matweb.com.
Brass is made by adding zinc to copper. Hold the solid metal over the melted copper until it starts dripping, then firmly drop it into the melt and
stir vigorously. It will splatter. This procedure results in the least splatter. The worst thing you can do is let the zinc float on top of the
melt and sputter away. It needs to be stirred quickly. Use a slag cover to reduce evaporation.
As the melting point falls (towards the end of the addition, maybe >20% Zn), you will have to worry less about splatter.
Tim
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Zinc
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| Quote: | Originally posted by 12AX7
What the devil does aluminum have to do with brass?
Tim |
I don't know. I just want to know if Cu dissolves in molten Al. Does it?
| Quote: | Originally posted by 12AX7
Brass is made by adding zinc to copper. Hold the solid metal over the melted copper until it starts dripping, then firmly drop it into the melt and
stir vigorously. It will splatter. This procedure results in the least splatter. The worst thing you can do is let the zinc float on top of the
melt and sputter away. It needs to be stirred quickly. Use a slag cover to reduce evaporation.
Tim |
So I can't add solid Cu to molten Zn and wait for it to dissolve?
[Edited on 28-6-2007 by Zinc]
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not_important
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Zinc's boiling point is below the melting point of copper, you tend to lose a lot of zinc when you keep it very hot. It might work if the copper were
in small peices, to maximise the surface area. Brass was once made by reducing zinc ores along with copper ores, or in the presence of metallic
copper. The zinc would vapourise and diffuse into the copper, this method was used until the technology of producing metallic zinc was developed.
Yes, copper dissolves in aluminium. At one time aluminium bronze was made by electrolysing molten salts containing aluminium compounds, using copper
electrodes. The copper would dissolve in the aluminium being formed, resulting in a pool of the alloy at the bottom of the tank.
The solution of copper in aluminium is slow enough and has other problems. These days it seems to be common to melt copper and add some aluminium to
it to get a high copper alloy, which melts at a much lower temperature. That is added to molten aluminium to get the final alloy.
For many alloys the melting point is between the melting points of the two metals. At the lower end of the temperature range the higher melting point
metal may not be all that soluble in the alloy or other metal, to get a good mix you have to fully melt the mixture. These two effects mean that you
may have problems attempting to make alloys the way you want to.
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JohnWW
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I think that this ebook, posted recently on todoquimica.net by Persseux, is pertinent to this thread:
Metals Handbook Desk Edition
Second Edition 1998 | ISBN: 0871706547 | Publisher: ASM International | English | Format: PDF OCR | 23 MB | 2571 Pages
The Metals Handbook Desk Edition is intended to serve as a comprehensive single-volume reference source on the properties, selection, processing,
testing, and characterization of metals and their alloys. Although the information presented in this Volume is drawn principally from the 20 volumes
of the ASM Handbook series, it should not be considered simply an abridged version of the larger work. Instead, the Metals Handbook Desk Edition draws
upon the complete arsenal of ASM products--both print and electronic--as well as other key sources of information originating from other publications,
company literature, technical societies, and government agencies.
Download:
RS.com
http://rapidshare.com/files/39576841/M.H.Desk.Edition.rar
Mihd
http://mihd.net/6m49p1
Posted By: persseux | Date: 27 Jun 2007 08:15
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12AX7
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Copper metal dissolves poorly in aluminum and zinc primarily due to oxides interfering, and secondarily due to kinetics (it's relatively cold, isn't
it?). Therefore, a flux is needed. A lot easier to fuse the copper, add some aluminum or zinc (not both) to make your master alloy, then add that to
the finished product.
50%wt Al/Cu master alloy melts about the same temperature as aluminum, so is an excellent source. It is essentially the theta intermetallic. It is
quite brittle.
Tim
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Zinc
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I have heared that copper should be melted under a cover of charcoal. So when I add zinc to it to make brass do I have to remove the charcoal or stir
in the zinc with the charcoal that would later seperate and be easily skimed before pouring?
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12AX7
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Charcoal is preponderously bouyant in molten copper. Think about it 
Tim
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Zinc
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When I make brass do I have to melt the copper under a charcoal cover before I add zinc or not?
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12AX7
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If it works better with charcoal, then it does.
I mean really, think about it (did I say that before?), you're adding zinc, which is reactive and a deoxidizer, which is the purpose of the charcoal.
So is it really needed? Obviously, you can if you want to.
Tim
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ciscosdad
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Laves Intermetallics
Hi Tim,
I found your info on the Intermetallic compounds most interesting, and I have assiduously downloaded all the phase diagrams on that website. It also
took me on a bit of a detour trying to find out more about the Laves intermetallic compounds.
While I now know more than I did, the question that first came to mind is as yet unanswered.
How many (if any) of these Laves Intermetallics are as brittle and crumbly as the MgAl (and presumably MgZn). Is there anything one could look for in
the phase diagrams to identify this sort of behaviour? Have you made any of the MgZn?
Pardon my ignorance. My knowledge of metallurgy is very scanty. I have made the MgAl compound but no others.
I have speculated on the idea of using any of these easily powdered compounds that include Al as a means of obtaining extremely fine powders of the
associated metal.
eg Dissolve the MgAl in alkali (plus possible some chromate) to leave the Mg as obsecenely fine particles. If successful I guess it may be too fine
and reactive.
I believe the Raney Nickel catalyst is made in similar fashion, but have not explored that at all.
Do you have anything to add?
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12AX7
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MgZn is most assuredly brittle. I have made it myself; in a pyrotechnic mixture it is slightly more reactive than zinc, and much easier to powder as
I don't have a ball mill. I might say it's even more brittle than MgAl, but the residual hardness of each may be due to different alloying impurities
in my stock.
I've heard of Laves used in the context of precipitates for hardening, which is probably suitable. Most intermetallics interrupt deformation of the
surrounding matrix, improving its strength, almost regardless of the material's strength (but not necessarily of its shape, as can be seen in gray
cast iron, which consists of soft alpha ferrite with sharp-edged graphite flakes; contrast to ductile or malleable irons, where spheroidized graphite
does not impact the tensile strength).
Raney nickel is made by dissolving aluminum from nickel, which occurs with acid or base; magnesium can't ever be exposed to solution, base or
otherwise, due to its high reduction potential (in excess of aluminum's, even). If you know of a solvent and complexing agent which will dissolve
aluminum, leaving magnesium, you might have a shot.
Tim
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